Humidifying methods for humidifiers which humidify air include an evaporation method. Evaporative humidifiers perform humidification of air by causing the air to pass through a humidifying material having a water absorption function and thus allowing heat exchange between moisture contained in the humidifying material and an air flow to vaporize and evaporate, achieving humidification.
Conventionally, there have been demands for an enhancement of the humidifying performance of evaporative humidifiers and a long-term maintenance of the humidifying performance.
In order to satisfy the above issues, various methods and apparatuses have been considered.
For example, in a technique described in Patent Literature 1, concavities and convexities are formed on a surface of a porous metallic plate having a three-dimensional net-like structure, and a high-porosity part and a low-porosity part are formed in two directions in a dispersed manner. It is considered that, with this technique, a large amount of water for evaporation is supplied to an evaporation interface in a stable manner and uniform and rapid evaporation is able to occur from the whole surface.
Furthermore, in a technique described in Patent Literature 2, particles are held on a surface of a filter substrate material of an evaporating filter to form voids. It is considered that, with this technique, concavities, convexities, and voids formed by particles on the filter surface allow water to be held and released, humidification is carried out in a surface part of the evaporating filter, and a high humidifying performance can be achieved.